Esd detection on a touch input device

ABSTRACT

A touch sensitive device that detects the occurrence of an electrostatic discharge event on the device by analyzing an acquired touch image for characteristics associated with the occurrence of an ESD event is provided. An acquired touch image is analyzed for characteristics that differentiate it from a touch image generated by a user input and are correlated with an expected touch image generated by an ESD event.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/710,318 (now U.S. Publication No. 2014/0071092), filed Dec. 10, 2012,which claims benefit of U.S. Provisional Patent Application No.61/699,176, filed Sep. 10, 2012, the entire disclosure of which isincorporated herein by reference for all purposes.

FIELD OF THE DISCLOSURE

This relates generally to the use of specialized sensors placed invarious locations on a touch input device to detect for the presence ofan electrostatic discharge (ESD) event occurring on the device.

BACKGROUND OF THE DISCLOSURE

Many types of input devices are available for performing operations in acomputing system, such as buttons or keys, mice, trackballs, joysticks,touch sensor panels, touch screens, and the like. Touch screens, inparticular, are becoming increasingly popular because of their ease andversatility of operation as well as their declining price. Touch screenscan include a touch sensor panel, which can be a clear panel with atouch-sensitive surface, and a display device such as a liquid crystaldisplay (LCD) that can be positioned partially or fully behind the panelso that the touch-sensitive surface can cover at least a portion of theviewable area of the display device. Touch screens generally allow auser to perform various functions by touching (e.g., physical contact ornear-field proximity) the touch sensor panel using a finger, stylus orother object at a location often dictated by a user interface (UI) beingdisplayed by the display device. In general, touch screens can recognizea touch event and the position of the touch event on the touch sensorpanel, and the computing system can generate touch images and theninterpret the touch images in accordance with the display appearing atthe time of the touch event, and thereafter can perform one or moreactions based on the touch image.

Electronic devices in general can be susceptible to electrostaticdischarge (ESD) events, which in general are caused by objects externalto the device imparting electrostatic energy onto the device. In theinstance of touch input devices, ESD events can generate a “false touch”on the touch screen; in other words, the device will think that a touchor proximity event has occurred when none exists. Furthermore, ESDevents can also cause a device to ignore an actual touch or proximityevent. For example, mutual capacitance touch sensor panels can be formedfrom a matrix of drive and sense lines of a substantially transparentconductive material such as Indium Tin Oxide (ITO). The lines are oftenarranged orthogonally on a substantially transparent substrate. An ESDevent can be coupled into the matrix of drive lines and sense lines,causing signals to appear that can be misinterpreted as a touch orproximity event. Also, ESD events can be coupled into the matrix ofdrive and sense lines causing signals to appear as negative touches,such that when a real touch occurs, it is missed. The false touches ormissed touches can lead to an overall degradation of the user experiencein that the device will register touches that the user did not intendand furthermore may miss actual touches intended by a user of thedevice.

SUMMARY OF THE DISCLOSURE

This relates to a touch input device that can be configured withdedicated ESD sensors placed on the touch input device to detect thepresence of an ESD event occurring on or in proximity to the device.

By taking advantage of known spatial and timing characteristics of anESD event that manifest themselves on touch images acquired by a touchinput device, the device is able to detect the occurrence of an ESDevent and can subsequently ignore any touch data collected during theoccurrence of the ESD event.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an exemplary touch sensor panel in a no-touchcondition according to disclosed examples.

FIG. 2 illustrates an exemplary touch image map in a no-touch conditionaccording to disclosed examples.

FIG. 3 illustrates an exemplary sensing circuit of a touch sensor panelaccording to disclosed examples.

FIG. 4 a illustrates an exemplary device incorporating a touch sensorpanel with an ESD event occurring on the touch sensor panel according todisclosed examples.

FIG. 4 b illustrates an exemplary device incorporating a touch sensorpanel with an ESD event occurring proximal to the touch sensor panelaccording to disclosed examples.

FIG. 5 a illustrates an exemplary comparison between the magnitude of atouch signal and the magnitude of an ESD event according to disclosedexamples.

FIG. 5 b illustrates another exemplary comparison between the magnitudeof a touch signal and the magnitude of an ESD event according todisclosed examples.

FIG. 6 a illustrates an exemplary set of drive lines and sense linesthat have a bonding layer selectively applied to them according todisclosed examples.

FIG. 6 b illustrates an exemplary touch image according to disclosedexamples.

FIG. 7 illustrates an exemplary multi-stimulation touch sensor panelaccording to disclosed examples.

FIG. 8 illustrates an exemplary set of stimulation steps at variousmoments in time for a multi-stim touch sensor panel according todisclosed examples.

FIG. 9 illustrates an exemplary method for determining the occurrence ofan ESD event on a touch sensor panel.

FIG. 10 illustrates an exemplary ESD scan procedure according to somedisclosed examples.

FIG. 11 illustrates an exemplary method to detect an ESD event using abasis vector of a multi-stim procedure according to some disclosedexamples.

FIGS. 12 a AND 12 b illustrate an exemplary method to count the numberof positive and negative elements in a touch image according to somedisclosed examples.

FIG. 13 illustrates exemplary computing system that can include one ormore of the examples described above.

FIGS. 14 a-14 d illustrate various electronic devices that can includeone or more of the examples described above.

DETAILED DESCRIPTION

In the following description of examples, reference is made to theaccompanying drawings which form a part hereof, and in which it is shownby way of illustration specific examples that can be practiced. It is tobe understood that other examples can be used and structural changes canbe made without departing from the scope of the disclosed examples.

This relates to the use of touch images generated by a touch sensorpanel to detect the presence of an ESD event. By taking advantage ofunique signal characteristics associated with ESD events, and by takingadvantage of the unique touch images that are generated due to thosecharacteristics, a touch sensitive device may be able to discern than anESD event has occurred and can choose to ignore any touch data receivedduring the ESD event.

Although examples disclosed herein may be described and illustratedherein in terms of mutual capacitance touch sensor panels, it should beunderstood that the examples are not so limited, but are additionallyapplicable to self-capacitance sensor panels, and both single andmulti-touch sensor panels in which the fabrication of conductive tracesis required.

FIG. 1 illustrates an exemplary touch sensor panel in a no-touchcondition, i.e., when there are presently no touches at the panel,according to various examples. In the example of FIG. 1, touch sensorpanel 124 can include an array of pixels 126 that can be formed at thecrossings of rows of drive lines 101 (D0-D3) and columns of sense lines102 (S0-S3). Each pixel 126 can have an associated mutual capacitanceCsig 114 when the drive line 101 forming the pixel is stimulated with astimulation signal Vstm 116. Each pixel 126 can also have an associatedstray capacitance Cstray when the drive line 101 forming the pixel isnot stimulated with a stimulation signal Vstm 116 but is connected toDC. In this example, drive line D0 can be stimulated with stimulationsignal 116 (Vstm), forming mutual capacitance Csig 114 at the pixels 126formed between the drive line D0 and the crossing sense lines S0-S3. Oneor more drive lines 101 can be stimulated at a time.

FIG. 2 illustrates an exemplary touch map of a touch sensor panel in ano-touch condition according to various examples, wherein touchesdetected in increasing amounts would symbolically register in thez-direction as shown by the arrow indicating increasing touch datavalues. In the example of FIG. 2, drive lines D0-D3 of a touch sensorpanel can be individually and/or simultaneously stimulated withstimulation signal(s) Vstm. Since there are no fingers (or otherobjects) touching the pixels 126 formed by the drive lines D0-D3 and thecrossing sense lines S0-S3, there is nothing to block some of theelectric field lines formed when the drive lines are stimulated so as toreduce the mutual capacitance Csig by an amount ΔCsig. As such, thetouch map can remain substantially flat at the pixels 126 to indicate notouch.

Referring again to FIG. 1, when a grounded user's finger (or otherobject) touches the panel 124, the finger can cause the capacitance Csig114 to reduce by an amount ΔCsig at the touch location as previouslymentioned. This capacitance change ΔCsig can be caused by current orcharge from the electric field lines being shunted through the touchingfinger to ground. Touch signals representative of the capacitance changeΔCsig can be transmitted by the sense lines 102 to the sense circuitryfor processing. The touch signals can indicate the pixel 126 where thetouch occurred and the amount of touch that occurred at that pixellocation.

FIG. 3 illustrates an exemplary sensing circuit of a touch sensor panelaccording to disclosed examples. Drive line 101 can be stimulated bystimulation signal 116. Stimulation signal 116 can be capacitivelycoupled to sense line 102 through the mutual capacitance 114 betweendrive line 101 and the sense line. When a finger or object 322approaches the touch node created by the intersection of drive line 101and sense line 102, the mutual capacitance 114 can be altered. Thischange in mutual capacitance 114 can be detected to indicate a touch orproximity event. The sense signal coupled onto sense line 102 can thenbe received by sense amplifier 324. Sense amplifier 324 can includeoperational amplifier 304, and at least one of a feedback resistor 310and a feedback capacitor 312. FIG. 3 is shown for the general case inwhich both resistive and capacitive feedback elements are utilized. Thesense signal can be inputted into the inverting input (referred to asVin) of the operational amplifier 304, and the non-inverting input canbe tied to a reference voltage Vref 306. The operational amplifier 304can adjust its output voltage to keep Vin approximately equivalent toVref and therefore keep Vin constant or virtually grounded as to rejectstray capacitance Cs or any change thereof. Therefore, the gain of theamplifier can be mostly a function of the ratio of the signalcapacitance 114 and the feedback impedance, comprised of resistors 310and capacitor 312. The output of sense amplifier 304 Vout can be furtherfiltered and heterodyned or homodyned by being fed into a multiplier316, and multiplied with a local oscillator 318 to produce Vdetect. Oneskilled in the art will recognize that the placement of filter 314 canbe varied, and thus could be placed after multiplier 316, or two filterscan be employed, one before the mixer and one after the mixer. In someexamples, there can be no filter at all. The direct current (DC) portionof Vdetect can be used to detect if a touch or proximity event hasoccurred.

An ESD event occurring on the touch sensor panel and being coupled intothe sense signal pathway can be modeled by noise source 324 (Vnoise).During an ESD event, Vnoise 324 can inject a signal onto the sense line102. This injection can compromise the sense circuit's 300 ability toreliably detect the change in mutual capacitance 114. An ESD event caninject a signal that is both positive in amplitude as well as negativeand thus can cause the sense circuit 300 to register either a touchevent when no touch event exists, or can cause no touch to be registeredwhen a touch does exist. Furthermore, while not illustrated, an ESDevent can also be coupled into the signal pathway via the drive lineside of the sense circuit.

FIG. 4 a illustrates an exemplary device incorporating a touch sensorpanel with an ESD event occurring on the touch sensor panel according todisclosed examples. As illustrated, a device 400 that contains a touchsensor panel 408 can have an ESD pulse 404 imparted directly on thetouch sensor by an object 402. The ESD pulse 404 can be coupled onto thesense circuitry of the touch sensor panel as described above.

FIG. 4 b illustrates an exemplary device incorporating a touch sensorpanel with an ESD event occurring proximal to the touch sensor panelaccording to disclosed examples. As illustrated, device 400 containingtouch sensor panel 408 can have an ESD pulse 406 that is impartedproximal to but not directly onto a touch sensor panel 408. While theESD pulse 406 may be directed towards circuitry that is not part of thesensing circuitry described in FIG. 3, the electrical layout of device400 may provide coupling pathways onto the sensing circuitry that can bemodeled by the circuit diagram illustrated in FIG. 3.

The location of an ESD event can in some instances create a signal thatcan be distinguished from an expected touch signal due to the differencein magnitude of an ESD pulse and a touch signal. Thus an ESD event canbe detected merely by noting the intensity of the signal received by thesense circuitry.

FIG. 5 a illustrates an exemplary comparison between the magnitude of atouch signal and the magnitude of an ESD event according to disclosedexamples. As illustrated, the magnitude of a touch signal depicted bybar 502 can be smaller than the magnitude of an ESD event depicted bybar 504. In this example, since an ESD event is larger in magnitude thana touch signal, the device can distinguish between ESD events and touchevents simply by noting the magnitude of the signal outputted by thetouch sensing circuitry. If a detected signal exceeds a pre-determinedthreshold, then the device can determine that the signal was caused byan ESD event.

FIG. 5 b illustrates another exemplary comparison between the magnitudeof a touch signal and the magnitude of an ESD event according todisclosed examples. In this example, the magnitude of the ESD signaldepicted by bar 506 is smaller than the magnitude of a touch signal. Inthis example, since an ESD event is smaller in magnitude than a touchsignal, the device can distinguish between ESD events and touch eventssimply by noting the magnitude of the signal outputted by the touchsensing circuitry. If a detected signal falls below a pre-determinedthreshold, then the device can determine that the signal was caused byan ESD event.

In some examples, the configuration of a touch sensitive device can bealtered in order to increase the difference in magnitude between a touchsignal and an ESD signal. For example in order to make the magnitude ofan ESD event smaller, capacitive shielding can be applied to the deviceso that less energy from an ESD event can be coupled into the sensingcircuitry. In another example, if a higher magnitude of an ESD signal isdesired so that it can be distinguished from a touch signal, the devicecan increase the capacitive coupling of an ESD event onto the sensecircuitry by, for instance, removing grounding guards on the device,making a cover glass on the device thinner, or by widening the gapbetween drive lines and sense lines at areas that are vulnerable to ESDevents.

However, despite the measures above, in some instances a touch signalcannot be distinguished from an ESD event based on magnitude, and thusanother characteristic of an ESD signal can be used to distinguish theESD event from an actual touch signal. For instance, ESD events can becoupled into the sense signal pathway via specific features of the touchsensor panel. For instance an ESD event can be coupled into the sensesignal pathway via a bondpad that is applied to various locations in thetouch sensor panel to bond the individual layers of a touch sensor paneltogether. The bondpads can be configured in a distinct pattern such thatthe touch sensitive device can discern a touch from an ESD event.

FIG. 6 a illustrates an exemplary set of drive lines and sense linesthat have a bondpad arrangement according to disclosed examples. In thisexample, the bondpads 608 can be arranged so that they correspond toevery other drive line such that there exists one set of drive lines 602that have bondpads, and another set of drive lines 604 that do not havebondpads. Each set of drive lines 602 and 604 can correspond to one setof sense lines 606.

FIG. 6 b illustrates an exemplary touch map during an ESD eventaccording to disclosed examples. As illustrated, the portions of thetouch map corresponding to drive lines 602 that have bondpads canregister a signal 612 that looks like a touch signal in response to anESD event since the ESD event can be coupled to the sense circuitry viadrive lines that have bondpads associated with them. As illustrated inFIG. 6 b, the portions 610 of the touch map that correspond to drivelines 604 that do not have bond pads may not register a signal since theenergy from an ESD event is not coupled into those particular drivelines. Since the bondpads are arranged such that they correspond toevery other row, a touch image caused by an ESD event can form adistinct pattern in which every other drive line can register a signaland the remaining drive lines can register no signal or a minimalsignal. Since a signal registered by a user's touch or by an object isusually continuous (a user's finger is not likely to stimulate everyother drive line), if a signal is registered by a device that has everyother drive line stimulated, the device can identify the signal as anESD event.

In some examples, the time characteristics of an ESD event can be usedto distinguish a touch input from an ESD event. For instance, the quickspeed (<200 μs) at which an ESD event appears and then disappears from atouch sensor panel can be used to distinguish an ESD event from a touchinput. For example, the timing characteristics of an ESD event can beused by a multi-stimulation (multi-stim) touch sensor panel toselectively disregard certain touch data.

FIG. 7 illustrates an exemplary multi-stimulation touch sensor panelaccording to disclosed examples. In the example of FIG. 7, the panel 700can include a plurality of drive lines 704 and a plurality of senselines 706. An intersection of a drive line 704 and a sense line 706 candefine a node 702. FIG. 7 indicates the presence of a stray capacitanceCstray and a mutual capacitance Csig at each node 702 located at theintersection of a drive line 704 and a sense line 706 (although Cstrayand Csig for only one column are illustrated in FIG. 7 for purposes ofsimplifying the figure). Stimulation signals Vstim 716-1 through 716-ncan be simultaneously applied to the n drive lines 704, where n can beany integer. Each stimulation signal Vstim 716 can be at a differentphase, as will be explained later, and upon being applied to a driveline, can cause a charge Qsig=Csig*Vstim to be injected into the senselines through the mutual capacitance Csig present at the affected nodes.A change in the injected charge can be detected when a finger, palm orother object is present at one or more of the affected nodes. Thestimulation signals 716 can be sine waves or any other suitable waveformor combination of waveforms at a suitable frequency or phase, or acombination of frequencies and/or phases for stimulating the drive lines704. Note that although FIG. 7 illustrates drive lines 704 and senselines 206 as being substantially perpendicular, they need not be soaligned. As described above, each sense line 706 can be connected to asense channel (see FIG. 3).

An example voltage of Vstim 716 can be about 4.16V. An example phase ofVstim 716 can be either 0° or 180°, which can be determined according toexamples of the disclosure. A sense channel (see FIG. 3) having a chargeamplifier, including feedback capacitor Cfb and feedback resistor Rfb,can receive the charge generated by the applied stimulation signal Vstim716 and the signal capacitance Csig. The stray capacitance Cstray can berendered ineffective at the charge amplifier using the virtual groundingprovided by the feedback around the amplifier. An exemplary sensechannel is disclosed in U.S. application Ser. No. 11/649,998, filed Jan.3, 2007, the contents of which are incorporated by reference herein intheir entirety for all purposes.

All or most of the drive lines 704 can be simultaneously stimulated(“multi-stim”) according to examples of the disclosure. In multi-stim,charges Qsig can be generated by Vstim 716 and Csig for all of the drivelines. The total charge output Xout 716 may be the sum of all chargeinjected into the sense line by each stimulated drive line. The outputmay be the superposition of all stimulation signals Vstim 716 multipliedby each of the Csig values on the sense line. In one example, sense line706 can have some pixels 702 which are driven by stimulation signals 716having a phase of 0° and simultaneously have other pixels 702 which aredriven by stimulation signals 716 having a phase of 180°, although otherphases are possible.

While the stimulation signals drive the drive lines, the signalcapacitance for each pixel may have a certain value Csig. When a touchor hover event occurs, Csig for the affected pixels may reduce by anamount ΔCsig. This reduction may be detected in the panel output signal,thereby detecting the event.

Referring again to FIG. 7, signal capacitances Csig-1 through Csig-n canbe formed at the pixels 702 when stimulation signals Vstim 716-1 through716-n are applied to the n drive lines 704. Charges Qsig (not shown inFIG. 7) can be generated by the stimulation signals Vstim 716 and thesignal capacitances Csig, and injected onto one or more sense lines 706.FIG. 7 shows the signal capacitances Csig-1 through Csig-n for only onesense line. However, the signal capacitances for the other sense linesintersecting the same drive line may be roughly the same. For example,all the sense lines that intersect the first drive line may have signalcapacitance of about Csig-1 at the corresponding pixels; all the senselines that intersect the second drive line may have signal capacitanceof about Csig-2 at the corresponding pixels; and so on. Therefore, onlyone sense line need be considered here.

Each charge Qsig can be calculated as follows.

Qsig=Vstim*Csig  (1)

where Vstim is the stimulation signal applied to a drive line and Csigis the signal capacitance formed at the pixel defined by theintersection of that drive line with a sense line. The output Xout 716is the sum of the charges Qsig generated by the stimulation signals andthe signal capacitances at all the pixels on a particular sense line andcan be calculated as follows.

$\begin{matrix}{{Xout} = {\sum\limits_{i = 1}^{n}\; {{Qsig}(i)}}} & (2) \\{{Xout} = {\sum\limits_{i = 1}^{n}\; {{{Vstim}(i)}*{{Csig}(i)}}}} & (3)\end{matrix}$

where i is a summation index for drive lines 1 to n. Here, thestimulation signals Vstim and the output Xout can be measured and aretherefore known. The n values of Csig are not. However, the n unknownCsig values can be determined, e.g., using linear algebra concepts. Inorder to determine the n unknown Csig values, n equations may be neededto show the relationship between Vstim, Xout, and Csig (see, e.g.,Equation (3)). These n equations could be formulated by performing aseries of n steps where, during each step, a different set ofstimulation signals Vstim could be simultaneously applied to the drivelines of the panel, thereby generating Csigs, and the resulting outputXout from a sense line of the panel could be measured.

Matrices can be a convenient way to represent these n equations asfollows:

$\begin{matrix}{\begin{bmatrix}{X\; 1} \\{X\; 2} \\{X\; 3} \\\ldots \\{Xn}\end{bmatrix} = {\begin{bmatrix}{V\; 11} & {V\; 12} & {V\; 13} & \ldots & {V\; 1n} \\{V\; 21} & {V\; 22} & {V\; 23} & \ldots & {V\; 2n} \\{V\; 31} & {V\; 32} & {V\; 33} & \ldots & {V\; 3n} \\\ldots & \ldots & \ldots & \ldots & \ldots \\{{Vn}\; 1} & {{Vn}\; 2} & {{Vn}\; 3} & \ldots & {Vnn}\end{bmatrix} \times \begin{bmatrix}{C\; 1} \\{C\; 2} \\{C\; 3} \\\ldots \\{Cn}\end{bmatrix}}} & (4)\end{matrix}$

where the X matrix has elements X1 through Xn which represent Xoutmeasured from a particular sense line in steps 1 through n; the V matrixhas elements V11 through Vnn which represent Vstim applied to the drivelines in steps 1 through n, where each row represents the n stimulationsignals simultaneously applied to the n drive lines during a particularstep, each column represents a drive line to be stimulated, and eachelement represents a stimulation voltage; and the C matrix has elementsC1 through Cn which represent Csig formed at the pixels defined by theintersection of drive lines 1 through n and the particular sense line.In the case where Vstim can either be a signal with a phase of 0° or180°, the elements of the V matrix can be represented by a 1 and −1,with 1 corresponding to a signal with a 0° phase, and −1 correspondingto a signal with a 180° phase. For the purposes of illustration andsimplification, as an example if one assumes that there are only fourdrive lines and one sense line, thus giving way to four nodes, equation(5) can be simplified to be:

$\begin{matrix}{\begin{bmatrix}{X\; 1} \\{X\; 2} \\{X\; 3} \\{X\; 4}\end{bmatrix} = {\begin{bmatrix}{V\; 11} & {V\; 12} & {V\; 13} & {V\; 14} \\{V\; 21} & {V\; 22} & {V\; 23} & {V\; 24} \\{V\; 31} & {V\; 32} & {V\; 33} & {V\; 34} \\{V\; 41} & {V\; 42} & {{V\; 43}\;} & {V\; 44}\end{bmatrix} \times \begin{bmatrix}{C\; 1} \\{C\; 2} \\{C\; 3} \\{C\; 4}\end{bmatrix}}} & (5)\end{matrix}$

Thus, for instance, the output of the sense line during the first stepof the multi stim procedure can be represented by X1. X1 can berepresented as:

X1=V11xC1+V12xC2+V13xC3+V14xC4  (6)

The multi-stim procedure can assume that C1-C4 stays constant during theentire multi-stim scan. When there is no touch, the values of C1-C4 canbe zero or close to zero. ESD events, however, can appear and thendisappear quickly relative to a touch signal (for instance <200 μs) andthus may only be present during one scan step of a multi-stim scan.

FIG. 8 illustrates an exemplary series of steps in a multi-stim schemeto generate a touch image. In the example of FIG. 8, four drive lines814 intersect one sense line 812. At t1, which corresponds to the firststep of the multi-stim procedure, the values of V11, V12, V13 and V14can be set to −1, 1, 1, 1 respectively. At t2, which corresponds to thesecond step of the multi-stim procedure, the values of V21, V22, V23,V24 can be set to 1, −1, 1, and 1 respectively. At t3, which correspondsto the third step of the multi-stim procedure, the values of V31, V32,V33, and V34 can be set to 1, 1, −1, and 1 respectively. Finally, at t4,which corresponds to the fourth step of the multi-stim procedure, thevalues of V41, V42, V43 and V44 can be set to 1, 1, 1, and −1respectively. With the multi-stim procedure described above, equation(5) becomes:

$\begin{matrix}{\begin{bmatrix}{X\; 1} \\{X\; 2} \\{X\; 3} \\{X\; 4}\end{bmatrix} = {\begin{bmatrix}{- 1} & 1 & 1 & 1 \\1 & {- 1} & 1 & 1 \\1 & 1 & {- 1} & 1 \\1 & 1 & 1 & {- 1}\end{bmatrix} \times \begin{bmatrix}{C\; 1} \\{C\; 2} \\{C\; 3} \\{C\; 4}\end{bmatrix}}} & (7)\end{matrix}$

Each row of the Vstim matrix can be labeled as a basis vector for themulti-stim procedure. Thus equation (7) above contains four basisvectors:

[−1 1 1 1]

[1 −1 1 1]

[1 1 −1 1]

[1 1 1 −1]

When no touch is occurring on the panel, the values of C1-C4 can be zeroor close to zero, which means that the values of X1-X4 will also be zeroor close to zero. During a touch event, the multi-stim procedure can becompleted in a speed that is quicker than the user's ability to changethe touch input and thus C1-C4 can be constant throughout the entiremulti-stim procedure. However, an ESD event can occur with a speed suchthat it only appears during one step in the multi-stim procedure. In oneexample using the multi-stim procedure of equation (7), if no-touch isoccurring on the touch sensor panel, but an ESD event occurs during thethird step of the multi-stim, then X1, X2 and X4 will be zero or closeto zero while X3 can equal:

$\begin{matrix}{{X\; 3} = {\begin{bmatrix}1 & 1 & {- 1} & 1\end{bmatrix} \times \begin{bmatrix}{C\; 1} \\{C\; 2} \\{C\; 3} \\{C\; 4}\end{bmatrix}}} & (8)\end{matrix}$

where C1-C4 represents the effect of an ESD event on a touch sensorpanel. A touch sensor panel using multi-stim can detect when a signalappears only during some of the steps in the multi-stim procedure todetermine that an ESD event occurs.

In an example where a touch signal and ESD event occur during amulti-stim cycle, C1-C4, instead of being zero or close to zero, canrepresent the amount of touch at each touch node. If an ESD event occursduring step 3 of the multi-stim procedure, then X3 can equal:

$\begin{matrix}{{X\; 3} = {\begin{bmatrix}1 & 1 & {- 1} & 1\end{bmatrix} \times \begin{bmatrix}{{C\; 1} + E} \\{{C\; 2} + E} \\{{C\; 3} + E} \\{{C\; 4} + E}\end{bmatrix}}} & (9)\end{matrix}$

E in equation (9) can represent an ESD signal appearing on the touchsensor panel. A touch sensor panel can detect the change in value of thetouch signal during one step of the multi-stim procedure to determinethat an ESD event has occurred.

During a normal touch operation, each basis vector can be applied to thetouch input to develop a composite image of touch. However, during anESD event, since the event can span the duration during which only onebasis vector is being applied, the composite image can be stronglycorrelated to one basis vector. Thus, in order to determine theoccurrence of an ESD event, a touch image's correlation to a basisvector can be analyzed. While the example above describes the ESDevent's duration as lasting during the application of one basis vector,one skilled in the art will recognize that an ESD event can occur over aplurality of basis vectors, for example 3 basis vectors. Even in theexample of 3 basis vectors, an ESD event can be distinguished from atouch event, since a touch event will present during the application ofall the basis vectors in a given multi-stim procedure.

FIG. 9 illustrates an exemplary method for determining the occurrence ofan ESD event on a touch sensor panel. Flowchart 900 begins with step 902in which the composite touch image is scanned to ensure that all valuesare above a pre-determined threshold magnitude. This can be done toensure decreasing the likelihood of false positive ESD readings.

If the magnitude of all the values in the touch image are above thepre-determined threshold magnitude then the method moves to step 904,but if not, the method can exit without detection of an ESD event. Atstep 904, each adjacent pixel pair in the touch image can be checked tosee if an opposite sign pair pattern can be detected. For instance,using the four pixel example, adjacent pixel pairs could consist of thefirst pixel and the second pixel, or the second pixel and the thirdpixel, or the third pixel and the fourth pixel. An opposite sign pairmeans that the adjacent pixels have an opposite amplitude, for instance[−500, 500] or [−40, 40], etc. Checking for a an opposite sign pairpattern can be indicative of an ESD value because an ESD signal tends tobe constant or relatively flat in amplitude, while in a four basisvector multi-stim procedure, each vector has only one opposite sign pairpattern. For instance, using the third basis vector as an example:

[1 1 −1 1]pixels 2 and 3 and pixels 3 and 4 have an opposite sign pair pattern. Inthe first basis vector, the opposite sign pair would be on pixel 1 and2, etc. If an ESD event occurs during the third step of the multi-stimprocedure and, for example, the ESD event has an amplitude of +500, thenthe composite touch image using equation (5) becomes:

$\begin{matrix}\begin{bmatrix}500 \\500 \\{- 500} \\500\end{bmatrix} & (10)\end{matrix}$

If no opposite sign pair is established, the method can be exitedwithout detection of an ESD event. If an opposite sign pair is detected,then the method can move to step 906 in which the opposite sign pair canbe analyzed to see if it is within a pre-determined tolerance. Thepurpose of checking tolerances is to distinguish an opposite sign pairfrom ungrounded objects that can generate negative pixel patterns. SinceESD signals can be relatively flat, the opposite sign pair should beclose to being equidistant from zero. In one example, a tolerance can becalculated using the following equation:

∥pixel 1|−|pixel 2∥/max{|pixel 1|,|pixel 2|}<pre-determined tolerance %

For example, if the pre-determined tolerance is equal to 4%, using theresult listed in equation (10) the tolerance check would yield thefollowing:

∥500|−|−500∥/max{|500|,|−500|}=0/500<4%

Thus, the above example would be within tolerance and could then move tostep 910 indicating that an ESD event has occurred. In another example,suppose the result obtained during the scan was [500 500 −90 500]; usingthis result and testing the tolerance would yield:

∥500|−|−90|/max{|500|,|−90|}=410/500=82%

Since 82% is greater than the pre-determined tolerance limit of 4%, theresult would be deemed out of tolerance and the method can exit withoutdetection of an ESD event.

In some examples, the method described above can be combined with amethod that takes advantage of the spatial characteristics of an ESDevent in order to decrease the likelihood of a false ESD eventdetection. If for instance, if it can be empirically determined that anESD signal when asserted occupies a space of four touch nodes, forexample, then a touch sensor panel can use that empirically determinedcharacteristic to perform a scan of the touch sensor panel to detect anESD event.

FIG. 10 illustrates an exemplary ESD scan procedure according to somedisclosed examples. While this example assumes that an ESD will occupyfour touch nodes, the disclosure is not so limited and can be modifiedto include ESD events that occupy more or less nodes. At step 1002, fourrows corresponding to one sense line can be scanned for ESD using themethods described above in the discussion pertaining to FIG. 7 and FIG.8, or any other method for detecting an ESD event discussed herein. Atstep 1004, if an ESD event is detected, in order to check for falsepositives, the procedure can then move to steps 1008 and 1010. If noevent is detected, then the procedure can move to step 1006 and anotherfour rows can be scanned. At step 1008, the four rows immediately abovethe four rows in which an ESD event was detected can be scanned usingthe procedure outlined in FIGS. 7 and 8. Also at step 1010, the fourrows immediately below the four rows in which an ESD event was detectedcan be scanned using the procedure outlined in FIGS. 7 and 8. At step1012, if the rows immediately above are found to not have an ESD event,in other words only background noise is detected (only contains valuesbelow a preset noise floor), or if there are no rows above (i.e. therows above are off the touch sensor panel), and if the rows immediatelybelow are found to not have an ESD event or if there are no rows below(i.e. the rows below are off the touch sensor panel), the procedure canmove to step 1014. In step 1014, the touch sensor panel can determinethat an ESD event has occurred since the ESD event is confined only tothe original four rows being scanned, which is what would be expectedbased on the spatial characteristics of an ESD event. If the outcome ofstep 1012 is false, then the procedure can move to step 1016. At step1016, if either the rows above register an ESD event, or the rows belowregister an ESD event, then an ESD event can be detected. If not, thenthe procedure can move back to step 1006, or in other examples canterminate.

While the method above can pertain to touch sensor panels that utilize afour element basis vector to perform a multi-stim procedure, thecharacteristics of basis vectors of a multi-stim procedure using adifferent number of elements in the basis vectors can be used to detectan ESD event. For instance if a touch sensitive device utilizes a 20step multi-stim procedure such that a basis vector contains 20 elements,then a distinguishing characteristic of an individual basis vector canbe used. For instance, if it is known that the basis vectors contain anequal number of 0° and 180° Vstim signal, then an example basis vectorcan be:

[1 −1 −1 1 −1 −1 −1 −1 1 1 1 1 1 −1 −1 1 1 1 −1 −1]

Using equation (4) and assuming that there is no signal during the othersteps in a multi-stim procedure, and that the signal amplitude of theESD event is 500, then the detected touch image along a column canalternate between 500 and −500, with both values appearing in thedetected touch image an equal number of times. Using the fact that abasis vector in a 20 element multi-stim procedure can produce a touchimage during an ESD event that has equal negative and positive values,one can detect the occurrence of an ESD event.

FIG. 11 illustrates an exemplary method to detect an ESD event using abasis vector of a multi-stim procedure. At step 1102, a touch image ofthe panel is created by using the capacitive signals detected by thetouch sensor panel. The detected touch image can be scanned to determineif a signal exists on the touch image being scanned. At step 1122, onecolumn of the touch image is selected. The selected column is thenscanned to detect if a signal exists on the column. In one example, asignal along a column can be detected using the formula:

$\begin{matrix}{{{{Ab\_}{sum}}_{j}\text{/}\# \mspace{14mu} {of}\mspace{14mu} {rows}} > {{pre}\text{-}{determined}\mspace{14mu} {value}}} & (11) \\{{{Where}\mspace{14mu} {Absumj}} = {\sum\limits_{i = 1}^{n}\; {{Qsigij}}}} & (12)\end{matrix}$

In the formula above, Qsig(ij) can represent the received signal at arow i and a column j. When the absolute value of each signal appearingon a node for a given column is summed over the entire column, and thatvalue is divided by the number of rows in the column, at step 1104 ifthe result is above a pre-determined threshold then the device can knowthat a signal has been detected on the selected column, as opposed to nosignal being received which would be expected if there were no touch orESD events occurring on the panel. If no signal is detected, then themethod can move to step 1114, and increment a counter that indicates howmany neutral columns exist in the touch image. The pre-determinedthreshold can be determined based on the noise environment of the touchsensor panel. Once a signal is detected, the method can move to step1106 where the number of positive and negative elements can bedetermined. As discussed above, in this example since the number ofpositive and negative phases in a basis vector are equal, and since ESDevents tend to have a relatively constant amplitude, a detected touchimage during an ESD event can appear similar to a basis vector of themulti-stim procedure in which the signal over a column can appear tohave a constant magnitude with the amplitude having both positive andnegative values in proportion to the number of positive and negativevalues of the basis vector. In this example, an ESD event occurring withan amplitude of 500 can produce a touch image that contains ten signalsthat are approximately 500 and ten signals that are approximately −500.At step 1106, the number of positives and negatives can be tabulated andif they are equal then method can move on, but if not then the methodcan move to step 1118 in which a counter that counts the number ofnegative columns is incremented. A negative column can mean that thedetected signal on the column is unlikely to be an ESD event.Mathematically speaking, the operation performed can be described as:

$\begin{matrix}{{{Positive}\mspace{14mu} {count}} = {{\sum\limits_{i = 1}^{n}\; {{Qsig}({ij})}} > 0}} & (13)\end{matrix}$

If the positive count=numbers of rows in the scan divided by two, thenthe positive and negative counts are equal which can mean that an ESDevent has occurred. However, due to the presence of noise, in someexamples a signal that would have otherwise been positive may be changedto negative due to noise; thus, in some examples the following test canbe used to determine if the number of positive and negative elements inthe touch image are indicative of an ESD event:

[Number of rows/2]−n<positive count<[Number of rows/2]+n  (14)

In the example of a column with 20 rows as above, and n=2, if thepositive count is between 8 and 12 then the signal will pass the testand move on to the next step, which in some examples can mean that anESD event is detected, while in other examples as explained below canrequire further testing.

In another example, in order to combat the noise on the touch sensorpanel changing measured touch image values from positive to negative (orvice versa) and thus corrupting the positive count, the methodillustrated in FIG. 12 a and FIG. 12 b can be employed. In this examplea six element touch image is used, but the method can be applicable toany touch image. The touch image at 1202 can be obtained using themethod discussed above. As shown, touch image 1202 contains fournegative elements and 2 positive elements, and thus would not have anequal positive and negative count. At step S1204 and shown at 1204, thedata can be sorted from negative to positive. At step S1206 and shown at1206, values that are determined to be within a pre-determined distanceaway from zero can be identified. Values close to zero can be especiallyvulnerable to noise, and thus a positive value that is close to zero canbe corrupted by noise to appear as a negative value. At 1206, theelements −6 and −1 can be identified as close to zero. The algorithm canconsider those values to be either a positive value or a negative value,since their distance from zero can make them vulnerable to noise thatcan change their sign. At S1208, the algorithm can determine if thepositive values are equal to the negative values, allowing for thevalues that were deemed to be close to zero to act as either a positiveor a negative value. Thus, at 1208 there are three negative values andthree positive values since −1 can be considered as a positive value.

Returning to FIG. 11, if the number of positive elements in the columncan be found to equal or substantially equal the number of negativevalues in the column, then the method can, in some examples, signal thatan ESD event has occurred. In other examples, the method can move tostep 1110 to perform an ESD magnitude grouping check. An ESD groupingmagnitude check can be performed to ensure that an actual touch eventoccurring on the touch panel is not mistaken for an ESD event, due tothe fact that the touch produced a touch image that has an equal numberof positive and negative elements. Generally, a touch signal will havesignal amplitudes across a column that vary in intensity. This can becontrasted with ESD signals that produce relatively flat amplituderesponses. An ESD magnitude grouping check can be performed to ensure auniformity in magnitude that can be indicative of an ESD event, and thuscan be distinguished from a touch event. In some examples, a subset ofadjacent elements within a touch image that has been sorted above can beselected. The subset can be analyzed to determine if the minimum andmaximum within the subset are within a pre-determined threshold distanceof each other. If the subset was generated in response to an ESD event,then the subset can have a relatively uniform magnitude and thus thedistance between the minimum and the maximum should be below thepre-determined threshold. All of the elements within the touch image canbe grouped into subsets of varying sizes and the check above can beapplied. If the ESD magnitude check determines that the magnitudes areuniform, then the method can move to step 1120 to increment a counterthat will count the column as a positive column, which can mean that thecolumn is indicative of an ESD event. If the ESD magnitude groupingcheck produces a negative result, then the method can move to step 1118and increment a counter that indicates that the signal on the column ismost likely not an ESD event.

After the column being scanned is classified as being neutral at 1114,or negative at 1118 or positive at 1118, the method can move to step1122 to determine if there are any more columns in the touch image thatare left to be scanned. If there are more columns to scan, then theprocess can move to step 1122 and select another column. If all thecolumns have been scanned, then the method can move to step 1126, wherethe count of positive and negative columns can be analyzed to determineif an ESD event has occurred. In one example, if the number of positivecolumns is greater than 0 and there are no negative columns detected,then the process can move to step 1128 and declare that an ESD event hasoccurred. If not then the method can move to 1130 and exit withoutdetecting an ESD event. In other examples, a different combination ofpositive columns vs. negative columns can be used to act as a thresholdfor determining whether or not an ESD event has occurred.

In all of the ESD detection methods above, since ESD events are unlikelyto happen while a user is already touching the device, the ESD detectionalgorithms described above can be disabled once a persistent touch hasbeen present on the touch sensor panel.

FIG. 13 illustrates exemplary computing system 1300 that can include oneor more of the examples described above. Computing system 1300 caninclude one or more panel processors 1302 and peripherals 1304, andpanel subsystem 1306. Peripherals 1304 can include, but are not limitedto, random access memory (RAM) or other types of memory or storage,watchdog timers and the like. Panel subsystem 1306 can include, but isnot limited to, one or more sense channels 1208 which can utilizeoperational amplifiers that can be configured to minimize saturationtime, channel scan logic 1310 and driver logic 1314. Channel scan logic1310 can access RAM 1312, autonomously read data from the sense channelsand provide control for the sense channels including calibrating thesense channels for changes in phase correlated with a parasiticcapacitance. In addition, channel scan logic 1310 can control driverlogic 1314 to generate stimulation signals 1316 at various frequenciesand phases that can be selectively applied to drive lines of touchsensor panel 1324. In some examples, panel subsystem 1306, panelprocessor 1302 and peripherals 1304 can be integrated into a singleapplication specific integrated circuit (ASIC).

Touch sensor panel 1324 can include a capacitive sensing medium having aplurality of drive lines and a plurality of sense lines, although othersensing media can also be used. Each intersection of drive and senselines can represent a capacitive sensing node and can be viewed aspicture element (node) 1326, which can be particularly useful when touchsensor panel 1324 is viewed as capturing an “image” of touch. Each senseline of touch sensor panel 1324 can drive sense channel 1308 (alsoreferred to herein as an event detection and demodulation circuit) inpanel subsystem 1306. The drive and sense lines can also be configuredto act as individual electrodes in a self-capacitance touch sensingconfiguration.

Computing system 1300 can also include host processor 1328 for receivingoutputs from panel processor 1302 and performing actions based on theoutputs that can include, but are not limited to, moving an object suchas a cursor or pointer, scrolling or panning, adjusting controlsettings, opening a file or document, viewing a menu, making aselection, executing instructions, operating a peripheral device coupledto the host device, answering a telephone call, placing a telephonecall, terminating a telephone call, changing the volume or audiosettings, storing information related to telephone communications suchas addresses, frequently dialed numbers, received calls, missed calls,logging onto a computer or a computer network, permitting authorizedindividuals access to restricted areas of the computer or computernetwork, loading a user profile associated with a user's preferredarrangement of the computer desktop, permitting access to web content,launching a particular program, encrypting or decoding a message, and/orthe like. Host processor 1328 can also perform additional functions thatmay not be related to panel processing, and can be coupled to programstorage 1332 and display device 1304 such as an LCD display forproviding a UI to a user of the device. Display device 404 together withtouch sensor panel 1324, when located partially or entirely under thetouch sensor panel, can form touch screen 1318.

Note that one or more of the functions described above can be performedby firmware stored in memory (e.g. one of the peripherals 1304 in FIG.13) and executed by panel processor 1302, or stored in program storage1332 and executed by host processor 1328. The firmware can also bestored and/or transported within any non-transitory computer-readablestorage medium for use by or in connection with an instruction executionsystem, apparatus, or device, such as a computer-based system,processor-containing system, or other system that can fetch theinstructions from the instruction execution system, apparatus, or deviceand execute the instructions. In the context of this document, a“non-transitory computer-readable storage medium” can be any medium thatcan contain or store the program for use by or in connection with theinstruction execution system, apparatus, or device. The computerreadable storage medium can include, but is not limited to, anelectronic, magnetic, optical, electromagnetic, infrared, orsemiconductor system, apparatus or device, a portable computer diskette(magnetic), a random access memory (RAM) (magnetic), a read-only memory(ROM) (magnetic), an erasable programmable read-only memory (EPROM)(magnetic), a portable optical disc such a CD, CD-R, CD-RW, DVD, DVD-R,or DVD-RW, or flash memory such as compact flash cards, secured digitalcards, USB memory devices, memory sticks, and the like.

The firmware can also be propagated within any transport medium for useby or in connection with an instruction execution system, apparatus, ordevice, such as a computer-based system, processor-containing system, orother system that can fetch the instructions from the instructionexecution system, apparatus, or device and execute the instructions. Inthe context of this document, a “transport medium” can be any mediumthat can communicate, propagate or transport the program for use by orin connection with the instruction execution system, apparatus, ordevice. The transport readable medium can include, but is not limitedto, an electronic, magnetic, optical, electromagnetic or infrared wiredor wireless propagation medium.

FIG. 14 a illustrates exemplary mobile telephone 1436 that can includetouch sensor panel 1424, the touch sensor panel including circuitry todetect and distinguish the presence of an ESD from a detected touchimage according to one disclosed example.

FIG. 14 b illustrates exemplary digital media player 1440 that caninclude touch sensor panel 1426, the touch sensor panel includingcircuitry to detect and distinguish the presence of an ESD from adetected touch image according to one disclosed example.

FIG. 14 c illustrates exemplary personal computer 1444 that can includetouch sensor panel (trackpad) 1428, the touch sensor panel and/ordisplay of the personal computer (in examples where the display is partof a touch screen) including circuitry to detect and distinguish thepresence of an ESD from a detected touch image according to onedisclosed example.

FIG. 14 d illustrates exemplary tablet computer 1448 that can includetouch sensor panel 1430, the touch sensor panel and/or display of thepersonal computer (in examples where the display is part of a touchscreen) including circuitry to detect and distinguish the presence of anESD from a detected touch image according to one disclosed example. Themobile telephone, media player and personal computer of FIGS. 14 a, 14 band 14 c can reduce the adverse effects on the detection of touch causedby an ESD event.

Although FIGS. 14 a-d discuss a mobile telephone, a media player, apersonal computer and a tablet computer respectively, the disclosure isnot so restricted and the touch sensor panel can be included on a tabletcomputer, a television, or any other device which can benefit from thereduction of adverse effects on the detection of touch caused by an ESDevent.

Therefore according to the above disclosure, some examples of thedisclosure are directed to a method for detecting an occurrence of anESD event on a touch input device, the method comprising: simultaneouslyapplying a plurality of stimulation signals to a plurality of drivelines of a touch sensor panel, wherein the stimulation signals areapplied in a multi-step sequence; acquiring a touch image of the touchsensor panel wherein the touch image consists of a plurality of sensedvalues; and analyzing the acquired touch image to determine acorrelation of the touch image to one or more steps in the sequence ofstimulation signals. Additionally or alternatively to one or moreexamples disclosed above, in other examples the multiple steps arestored in a matrix of vectors, the matrix having a plurality of basisvectors. Additionally or alternatively to one or more examples disclosedabove, in other examples the correlation of the touch image to one ormore steps in the sequence of stimulation signals further includes thetouch image being correlated to one or more of the plurality of basisvectors. Additionally or alternatively to one or more examples disclosedabove, in other examples the correlation between the touch image and theplurality of basis vectors is determined by comparing a first number ofpositive signals within the plurality of sensed values with a secondnumber of negative signals within the plurality of sensed values.Additionally or alternatively to one or more examples disclosed above,in other examples analyzing the acquired touch image includes: analyzinga first portion of the touch image corresponding to a first group ofdrive lines to determine a correlation of the touch image to the one ormore steps in the sequence of stimulation signals; analyzing a secondportion of the touch image corresponding to a second group of drivelines to determine a correlation of the touch image to the one or moresteps; and comparing the first portion of the touch image to the secondportion of the touch image. Additionally or alternatively to one or moreexamples disclosed above, in other examples acquiring a touch image ofthe touch sensor panel further includes receiving a plurality of signalsfrom a plurality of sense lines of the touch sensor panel, the pluralityof signals being indicative of a change in capacitance at a plurality oftouch nodes of the device. Additionally or alternatively to one or moreexamples disclosed above, in other examples the method further comprisesdisabling ESD detection when one or more user inputs have been detectedby the touch sensor panel.

Additionally or alternatively to the one or more examples disclosedabove, other examples of the disclosure are direct to a touch sensitivedevice capable of detecting the occurrence of an ESD event, the devicecomprising: a touch sensor panel capable of simultaneously applying aplurality of stimulation signals to a plurality of drive lines of thetouch sensor panel, wherein the stimulation signals are applied in amulti-step sequence; a processor capable of acquiring a touch image ofthe touch sensor panel, wherein the touch image consists of a pluralityof sensed values; and analyzing the acquired touch image to determine acorrelation of the touch image to one or more steps in the sequence ofstimulation signals. Additionally or alternatively to one or moreexamples disclosed above, in other examples the processor is furthercapable of storing the multiple steps in a matrix of vectors, the matrixhaving a plurality of basis vectors. Additionally or alternatively toone or more examples disclosed above, in other examples the processor isfurther capable of determining the correlation of the touch image to theone or more steps in the sequence of stimulation signals by correlatingthe touch image to one or more of the plurality of basis vectors.Additionally or alternatively to one or more examples disclosed above,in other examples the processor is further capable of determining thecorrelation between the touch image and the plurality of basis vectorsby comparing a first number of positive signals within the plurality ofsensed values with a second number of negative signals within theplurality of sensed values. Additionally or alternatively to one or moreexamples disclosed above, in other examples analyzing the acquired touchimage includes analyzing a first portion of the touch imagecorresponding to a first group of rows to determine a correlation of thetouch image to one or more steps in the sequence of stimulation signals;analyzing a second portion of the touch image corresponding to a secondgroup of drive lines to determine a correlation of the touch image tothe one or more steps; and comparing the first portion of the touchimage to the second portion of the touch image. Additionally oralternatively to one or more examples disclosed above, in other examplesacquiring a touch image of the touch sensor panel further includesreceiving a plurality of signals from a plurality of sense lines of thetouch input device, the plurality of signals being indicative of achange in capacitance at a plurality of touch nodes of the device.Additionally or alternatively to one or more examples disclosed above,in other examples the processor is further capable of disabling ESDdetection when one or more user inputs have been detected by the touchsensor panel.

Additionally or alternatively to the one or more examples disclosedabove, other examples of the disclosure are direct to a non-transitorycomputer readable storage medium having stored thereon a set ofinstructions for detecting ESD events in a touch sensor panel, that whenexecuted by a processor causes the processor to: simultaneously apply aplurality of stimulation signals to a plurality of drive lines of atouch sensor panel, wherein the stimulation signals are applied in amulti-step sequence; acquire a touch image of the touch sensor panelwherein the touch image consists of a plurality of sensed values; andanalyze the acquired touch image to determine a correlation of the touchimage to one or more steps in the sequence of stimulation signals.Additionally or alternatively to one or more examples disclosed above,in other examples the processor is further capable of storing themultiple steps in a matrix of vectors, the matrix having a plurality ofbasis vectors. Additionally or alternatively to one or more examplesdisclosed above, in other examples the processor is further capable ofdetermining the correlation of the touch image to the one or more stepsin the sequence of stimulation signals by correlating the touch image toone or more of the plurality of basis vectors. Additionally oralternatively to one or more examples disclosed above, in other examplesthe processor is further capable of determining the correlation betweenthe touch image and the plurality of basis vectors by comparing a firstnumber of positive signals within the plurality of sensed values with asecond number of negative signals within the plurality of sensed values.Additionally or alternatively to one or more examples disclosed above,in other examples analyzing the acquired touch image includes analyzinga first portion of the touch image corresponding to a first group ofrows to determine a correlation of the touch image to one or more stepsin the sequence of stimulation signals; analyzing a second portion ofthe touch image corresponding to a second group of drive lines todetermine a correlation of the touch image to the one or more steps; andcomparing the first portion of the touch image to the second portion ofthe touch image. Additionally or alternatively to one or more examplesdisclosed above, in other examples acquiring a touch image of the touchsensor panel further includes receiving a plurality of signals from aplurality of sense lines of the touch input device, the plurality ofsignals being indicative of a change in capacitance at a plurality oftouch nodes of the device. Additionally or alternatively to one or moreexamples disclosed above, in other examples the processor is furthercapable of disabling ESD detection when one or more user inputs havebeen detected by the touch sensor panel.

Although the disclosed examples have been fully described with referenceto the accompanying drawings, it is to be noted that various changes andmodifications will become apparent to those skilled in the art. Suchchanges and modifications are to be understood as being included withinthe scope of the disclosed examples as defined by the appended claims.

What is claimed is:
 1. A method for detecting an occurrence of an ESDevent on a touch input device, the method comprising: applyingstimulation signals to a plurality of drive lines of a touch sensorpanel; acquiring a touch image of the touch sensor panel wherein thetouch image comprises a plurality of sensed values based on thestimulation signals, the sensed values including an ESD valuecorresponding to and ESD event and touch values corresponding to one ormore touch events; differentiating the ESD event from the touch eventsby determining if a magnitude of the EDS values exceeds a predeterminedthreshold, wherein touch events have touch values lower than thepredetermined threshold.
 2. The method of claim 1, further comprisingremoving capacitive shielding from the touch input device to permit moreenergy from the ESD event to be coupled to the touch input device.
 3. Amethod for detecting an occurrence of an ESD event on a touch inputdevice, the method comprising: applying stimulation signals to aplurality of drive lines of a touch sensor panel; acquiring a touchimage of the touch sensor panel wherein the touch image comprises aplurality of sensed values based on the stimulation signals, the sensedvalues including an ESD value corresponding to and ESD event and touchvalues corresponding to one or more touch events; differentiating theESD event from the touch events by determining if a magnitude of the EDSvalues is lower than a predetermined threshold, wherein touch eventshave touch values higher than the predetermined threshold.
 4. The methodof claim 3, further comprising applying capacitive shielding to thetouch input device to permit less energy from the ESD event to becoupled to the touch input device.
 5. A touch sensitive device capableof detecting the occurrence of an ESD event, the device comprising: atouch sensor panel capable of applying stimulation signals to aplurality of drive lines of the touch sensor panel, a processor capableof acquiring a touch image of the touch sensor panel, wherein the touchimage comprises a plurality of sensed values based on the stimulationsignals, the sensed values including an ESD value corresponding to andESD event and touch values corresponding to one or more touch events;and differentiating the ESD event from the touch events by determiningif a magnitude of the EDS values exceeds a predetermined threshold,wherein touch events have touch values lower than the predeterminedthreshold.
 6. A touch sensitive device capable of detecting theoccurrence of an ESD event, the device comprising: a touch sensor panelcapable of applying stimulation signals to a plurality of drive lines ofthe touch sensor panel, a processor capable of acquiring a touch imageof the touch sensor panel, wherein the touch image comprises a pluralityof sensed values based on the stimulation signals, the sensed valuesincluding an ESD value corresponding to and ESD event and touch valuescorresponding to one or more touch events; and differentiating the ESDevent from the touch events by determining if a magnitude of the EDSvalues is lower than a predetermined threshold, wherein touch eventshave touch values higher than the predetermined threshold.
 7. A methodfor detecting an occurrence of an ESD event on a touch input device, themethod comprising: configuring a specific feature of the touch inputdevice that correspond to selected drive lines among a plurality ofdrive lines on the touch input device; applying stimulation signals tothe plurality of drive lines of a touch sensor panel; acquiring a touchimage of the touch sensor panel wherein the touch image comprises aplurality of sensed values based on the stimulation signals, the sensedvalues including an ESD value corresponding to and ESD event and touchvalues corresponding to one or more touch events; and differentiatingthe ESD event from the touch events by determining if the sensed valuesoccur only on the selected drive lines.
 8. The method of claim 7 whereinthe specific feature establishes a sense signal pathway to sensorcircuitry of the touch input device.
 9. The method of claim 7, whereinthe specific feature comprises bondpads corresponding to the selecteddrive lines.
 10. The method of claim 9, wherein the plurality of drivelines form rows and the selected drive lines comprise every other row ofdrive lines.
 11. A touch sensitive device capable of detecting theoccurrence of an ESD event, the device comprising: a touch sensor panelcapable of applying stimulation signals to a plurality of drive lines ofthe touch sensor panel, a processor capable of acquiring a touch imageof the touch sensor panel, wherein the touch image comprises a pluralityof sensed values based on the stimulation signals, the sensed valuesincluding an ESD value corresponding to and ESD event and touch valuescorresponding to one or more touch events; and differentiating the ESDevent from the touch events by determining if the sensed values occuronly on the selected drive lines.
 12. The touch sensitive device ofclaim 11, wherein the specific feature establishes a sense signalpathway to sensor circuitry of the touch input device
 13. The touchsensitive device of claim 11, wherein the specific feature comprisesbondpads corresponding to the selected drive lines.
 14. The touchsensitive device of claim 13, wherein the plurality of drive lines formrows and the selected drive lines comprise every other row of drivelines.